Road vehicles may be designed to travel through a body of water to a finite depth, which may be referred to as a maximum wading depth. Beyond this limit there is a risk that the vehicle engine and electronics may be damaged. Identifying that a vehicle has entered a wading situation or is in a wading event is advantageous so that control systems of the vehicle can be deployed.
WO-A-03/002378 discloses the use of ultrasonic parking distance control (PDC) sensors to determine the likelihood of a vehicle being at least partially immersed in a fluid, such as water. Due to the detection of an object at approximately zero distance by more than one parking sensor, in conjunction with the detection of other conditions, for example vehicle speed and user selected “off-road” state; the system disclosed in WO-A-03/002378 is configured to determine that a vehicle is likely to be in a wading situation. It is recognized however that the detection of an object by more than one parking sensor simultaneously may be for reasons other than a wading event and that it is desirable to have a more positive determination that a vehicle is in a wading situation.
The present invention seeks to provide an improvement in the field of liquid, (particularly, water), immersion detection systems that has particular application for vehicles. The invention may be utilised in applications other than for vehicles; for example, it is envisaged that embodiments of the invention may have application in buildings, for example domestic houses, where the automatic detection of water at a certain level may be useful. Such a system may be adapted, for example, to effect automatic deployment of flood defence systems.